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GM Hens and Medicinal Eggs
Overview The creation of medicinal chicken eggs by the Roslin Institutes's Helen Sang and her team was first successful in 2007, with the addition of complex proteins to the eggs that could be used to treat multiple sclerosis, skin cancer, and arthritis. These beneficial proteins are produced instead of the typical protein ovalbumin found within the egg white. The researchers found that in a flock of 500 of their genetically modified chickens, every egg produced contained miR24 (a human monoclonal antibody that may be able to treat malignant melanoma and arthritis), b-1a (a human interferon that acts as an antiviral drug and closely resembles current treatments for multiple sclerosis). The protein products may then be separated from the eggs and utilized by scientists in the treatment of diseases. In this experiment, the chickens are used as a living bioreactor, which allows for the repeated production of the transgenic eggs in a natural environment. Methods In order to add the desired protein products to the chicken eggs, researchers first had to alter the genome of roosters. The roosters selected for the experiment had been part of a trial group in which the gene coding for the protein product of choice was spliced into the roster's semen cells through the use of lentivirus vectors. The transformed sperm cells are then screened for in the group of roosters selected for this experiment. The transformed rooster was then bred with normal hens, producing a flock of chickens that contained the inserted gene sequence. These chickens were then able to produce eggs containing the protein products coded for by the inserted gene sequence. Goals Based on the current findings, the creation and use of medicinal eggs will hopefully become more widespread, with the experiment expanding to include the ability to produce other protein products as well. In addition to these possibilities, the use of this method has the potential to cut drug costs. Thanks to the use of chickens, it's possible to avoid the high cost of bacterial or other cells necessary for industrial bioreactors. Comparatively, the chickens are able to produce many eggs containing the desired protein products (up to 300 eggs a year) and are able to reproduce, are fairly cheap to care for, and increase the number of chickens within the flock that are able to produce the medicinal eggs. However, after a few generations, the protein product produced by the descendants of the original subjects are no longer useful - therefore only a certain number of offspring may be produced that still produce viable proteins. Risks Using the lentivirus as the delivery method has numerous risks, including the the possible integration of retroviruses in close proximity of potential oncogenes; if these oncogenes became activated, the cell would be converted into a tumor cell and continue to grow out of control. Additionally, the lentiviral vector is rather small, which limits the size of the possible transgene that could be introduced via this method. References Cheryl V. Hunter, Laurence S. Tiley, Helen M. Sang, Developments in transgenic technology: applications for medicine, Trends in Molecular Medicine, Volume 11, Issue 6, June 2005, Pages 293-298, Biello, David. "The Incredible, Medical Egg." Scientific American Global RSS. Scientific American, 16 Jan. 2007. Web. 05 Oct. 2014. . Jha, Alok. "GM Hens' Medicinal Eggs Aid Cancer Fight." The Guardian. The Guardian News, 14 Jan. 2007. Web. 5 Oct. 2014. . McGrew, Michael. "Efficient Production of Germline Transgenic Chickens Using Lentiviral Vectors." EMBOpress. EMBO, 07 Jan. 2004. Web. 05 Oct. 2014..